Compute Without a Calculator

Posted by Lifehacker US Edition at 8:00 AM on September 19, 2007

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Learn to calculate numbers quickly without a calculator with The List Universe's 10 arithmetic tricks. Using one of the mental shortcuts, you can calculate complicated operations in your head—handy when bigger numbers come into play. Here's one that's new to me:

If you need to square a 2-digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!
Got any favourite math tricks to add? Share them in the comments.

 

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